This invention relates to a muffler, more particularly, to a muffler for eliminating or reducing effectively the gas flow pulsation and the noise caused thereby.
A muffler is used to reduce noise by utilizing mainly aerodynamic attenuating principles, such as sound absorption, expansion, resonance and so on. The level of research and development associated with the structure and the principles of muffler design is very high. By patent searching it is found that in China alone the number of the patents associated with mufflers is more than 600. The mufflers in these patents are diverse, but they have a common ground, namely that the structures of the mufflers are unchangeable so that they can't be provided with a mechanism which is capable of realizing self-adjustment automatically with respect to change of the pulsating gas flow. Although there are some adjusting devices provided for them, these devices only can be adjusted manually. The sound-deadening characteristics of mufflers having unchangeable structure is unchangeable, but variation of pulsation of gas flow is random and the mufflers that have unchangeable structure are therefore always in a passive state of operation. Anechoic effect can therefore never be perfect. At present, there is still no muffler which can change positively with respect to the pulsating gas flow and realize self-adjustment. In practice, the muffler is normally used to reduce noise of discharging gas of reciprocating engines and gas compressors, which are originated from pulsation of discharging gas. Generally, it is more difficult to reduce or eliminate the pulsation in low-frequency and medium-frequency than that in high-frequency. At present, there is no novel, light-weighted and small-sized muffler which can reduce effectively gas flow pulsation in low-frequency.